This invention relates to the treatment of underground oil reservoirs. In one of its aspects this invention relates to the recovery of oil from a reservoir by treatment with a mixture of hydrocarbon gas and carbon dioxide. In another of its aspects this invention relates to a method for reducing the CO.sub.2 content of a hydrocarbon gas-CO.sub.2 mixture to produce hydrocarbon gas having a sufficient BTU content for use as fuel. In another of its aspects this invention relates to a method for separating CO.sub.2 and hydrocarbon gas from a mixture thereof. In yet another of its aspects this invention relates to the recovering of a CO.sub.2 enriched product gas from a CO.sub.2 -hydrocarbon gas mixture.
Many natural gas wells produce a hydrocarbon gas that contains carbon dioxide. Improved oil recovery projects in which CO.sub.2 is injected into a reservoir to displace oil produces a mixture of hydrocarbon gas and CO.sub.2. There are, therefore, produced hydrocarbon gas streams containing CO.sub.2 in amounts from traces up to about 98 percent of the total. While relatively small amounts of CO.sub.2 in a hydrocarbon gas stream are not harmful, relatively large amounts of CO.sub.2 sufficiently reduce the BTU content of the mixture so that it is not useful as a fuel gas.
It is therefore an object of this invention to provide a method for treating a mixture of hydrocarbon gas and carbon dioxide sufficiently to reduce the CO.sub.2 content to provide a resulting mixture that is useful as a fuel. It is another object of this invention to provide a method for treating an underground reservoir using a mixture of hydrocarbon gas and carbon dioxide. It is still another object of this invention to provide a method for separating hydrocarbon gas from a mixture of hydrocarbon gas and carbon dioxide to produce a stream of increased carbon dioxide content.
Other aspects, objects and the various advantages of this invention will become apparent upon reading the specification and the appended claims.